In vehicle fuel systems, an electrically driven fuel pump is mounted in a fuel reservoir which, in turn, is located in the main vehicle fuel tank. The pump has an outlet leading to a fuel rail which distributes operating fuel to fuel injection units in a fuel rail at the engine. In some fuel systems, the pump has a capacity greater than that required by the engine and a pressure relief valve discharges over-capacity fuel to a return line which dumps into the reservoir.
Also, in some systems, the fuel pump has a main outlet directed to the engine and a diversion outlet directed to a jet pump at the base of the reservoir. The jet pump has a fuel tank inlet, independent of the main pump inlet, which, in connection with a venturi passage, moves fuel into the reservoir to maintain a supply of fuel in the reservoir, independent of fuel in the main tank of the vehicle.
Some systems have provided for over flow of fuel from the reservoir to the main tank. However, the reservoir fuel may be hot due to the return flow and it is not desirable that hot fuel reach the main tank. Also, it is desirable that the reservoir be closed at the top to create a back pressure on the jet pump and accordingly increase the pressure at the main fuel inlet to provide a force feed to the main pump.